The last post covered Dr. Everett’s introductions; now we’re going to move on to part II of his testimony, titled “The Physics”. In this section he questions estimates of future acidification.

Dr. Everett never seriously challenges the 0.1 pH of acidification which has already occurred, or that human CO2 emissions are the cause (though he will in later sections challenge its impact). His purpose in this section is to challenge projections for future acidification, on the basis that less carbon dioxide will be emitted than is projected in the models used:

…if the projections we are concerned with today are based on the IPCC IS92a model, […] we should give the information on its impacts a second look.

IS92a is an emissions projection. It’s one possible route that we can take as a carbon-emitting global society, based in particular on the assumption that we simply continue current trends in carbon use. It’s called the “Business As Usual” scenario. Everett’s main claim in this section is that “the Business as Usual scenario has been overtaken by events” and that we aren’t going to go that route; one line of evidence he offers is a series of data tracking the rate of change in atmospheric carbon dioxide:

This would require the atmosphere to more than double the present rate of growth of CO2 to 3.05 ppm, yet the growth rate seems to be leveling off, if not declining (see chart below). […] The CO2 scenarios are literally falling flat and need revision. The observational trend line shows monotonic growth – pretty much a straight line as in the chart below of global marine CO2 measurements (NOAA data)4, while the IPCC scenarios used in most research rely on an accelerating growth. Certainly the predicted rapid acceleration of the IS92a model (see solid black line in middle of the figure on the right) is missing from the NOAA data plotted below. In fact, if the last 8 or 12 years are representative of the future, we might imagine a downward slope in the growth rate.

There’s a lot going on just in this one paragraph, and I’m not going to be covering it all in htis post. Let’s start off just by taking a look at the graph of CO2 measurements that he shows us:

This is the graph that Dr. Everett shows us of the rate of change in atmospheric carbon dioxide over time. Click for source data

Now, Everett has done some interesting things here: First of all, he’s stretched his graph so that it’s three times as long as it is tall. This makes the upward trend in the data look smaller, nay, nonexistent. When I replot the data with a 1:1 aspect ratio (the graph is as wide as it is tall) the trend sticks out, clear as day. (It’s even more obvious if you use the full data series, stretching back to 1959, but for now we can just focus on what Everett shows us. )

The rate of change in concentration of CO2 (red) over time. It's a rate, so the units are in parts per million per year The black line is a linear regression; the data have an upward trend with ~93% confidence.

It was probably just an unfortunate formatting decision, but presenting the data in this way, intentionally or not, hides the incline.

He does something else interesting: He shows us, on the one hand a graph of carbon dioxide growth rates and on the other hand a graph of carbon dioxide concentrations.

This is a graph of the concentration of atmospheric CO2 under various IPCC scenarios. The units of this graph are parts per million: it's a graph of concentration. IS92a is the black line.

And he switches back and forth between them almost without comment, as though they were graphs of the same thing: “Certainly the predicted rapid acceleration of the IS92a model (see solid black line in middle of the figure on the right) is missing from the NOAA data plotted below.” They’re graphs of related quantities, certainly, and they can be compared if you’re careful. But when you’re presenting to an audience of non-experts, rapidly switching between a quantity and its derivative is begging for misinterpretation. Surely someone, maybe even a senator, has looked uncritically at these graphs and thought they were comparing the same quantity.

In fact, a lot of what he says doesn’t make much sense at all, unless he’s expecting you to make that mistake. Here’s an example:

“Certainly the predicted rapid acceleration of the IS92a model […] is missing from the NOAA data plotted below.”

It is? There’s a statistically significant upward trend in the NOAA’s data. The data measure the rate of change in CO2 concentration per year, and an upward trend in the rate means an acceleration of concentrations- just as in IS92a. (It may be that the key word is ”rapid“, that the NOAA data don’t show a sufficiently strong upward trend, but that would take a more quantitative argument than simply directing our attention to a graph. And we’ll see later that these data actually agree relatively well with IS92a.)

Rate Data

Concentration Projections

Here’s another thing that wouldn’t otherwise make sense:

“The observational trend line shows monotonic growth – pretty much a straight line as in the chart below of global marine CO2 measurements (NOAA data)4, while the IPCC scenarios used in most research rely on an accelerating growth.”

The observational trend line of what? Of the concentrations, or of their rate of change? They’re two different things. We certainly do see monotonic growth in the rate (monotonic means that it either always increases or always decreases.) But that doesn’t help him any, because any growth in the rate (even if it’s a ”straight line“) means that the concentration is accelerating. It’s not at all clear how these two graphs are supposed to contrast.

There’s another claim in this paragraph that needs to be examined:

…the growth rate seems to be leveling off, if not declining […] In fact, if the last 8 or 12 years are representative of the future, we might imagine a downward slope in the growth rate.

Looking at the graphs, do you think that they support this claim? I don’t. To be continued….

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[…] seen one reason to doubt the linearity of CO2 data. Remeber back when we were talking about the rate of change in CO2 levels, and we found that the rate has increased over time? A linear growth in CO2 is characterized by a […]